Review of electrochemical production of doped graphene for energy storage applications

Graphene has been investigated and studied over the years due to its exceptional electrical, thermal, quantum and optical properties. A low-cost, simple, and environmentally friendly method to produce graphene is of great importance and such a method is required to fully exploit its physical and chemical properties for various applications. The present review reports the recent progress and developments on efficient methods for graphene synthesis, focusing primarily on the electrochemical exfoliation of graphite in inorganic salts or aqueous acids, assessing the method capabilities for mass production of doped electrochemically exfoliated graphene (EEG) for energy storage applications. A facile electrochemical exfoliation of graphite is typically carried out in a parallel two-electrode electrolytic cell system with aqueous inorganic salt-based electrolytes under ambient conditions. The nature of the EEG can be easily tuned by controlling the exfoliation conditions. Furthermore, the qualities of the graphene produced from the electrochemical exfoliation method using different electrolytes and setup parameters were reviewed comprehensively, regarding yield, chemical and physical properties (i.e., the morphology (layers and lateral size distribution), the nature and concentration of doped heterogeneous atoms, temperature stability, the degree of disorder, carbon/oxygen ratio, electrical conductivity (or sheet resistance), and the electrochemical performance in energy storage applications. Heteroatom doped EEG presents great promise for future design and large-scale production of affordable and high-performance composite electrodes for energy storage devices, e.g., hybrid supercapacitors, batteries, and full cells.